Support point clouds

[camnewnham]

This addresses #16 and brings atteneder/glTFast#135 to the 2020/MeshData api. Due to the new API the changes are also much simpler.

See atteneder/draco#2 for the draco component.
Note this PR doesn't include updated binaries (due to prior discussion of the security non-automated-created builds).

I haven't backdated the changes to the older API (!DRACO_MESH_DATA) and don't have a particular interest in doing so as it was significantly messier - I don't see this as an issue as it's a new feature for a new version.

Note vertex colors do not currently work for meshes or point clouds, I have added a separate issue to track this: #27

Happy to discuss!

[camnewnham]

@atteneder just bumping this, have you had a chance to have a look?

[atteneder]

Sorry for not replying...I was on paternal leave when you opened the PR. I'll have a look!

[atteneder]

@camnewnham Thanks for the repeated effort to get this done. I'll help you to land it this time.

Can you provide a draco compressed point cloud glTF (or a way to create them)? Never done that before.

Regards

[camnewnham]

Hi @atteneder, congrats on the new arrival! Bet you're going to be busy :)

Here's a draco-compressed GLTF containing points.
bunny_pts_color_draco.zip

In three.js:

In glTFast/Unity (this PR):

Note that:

• Point loading is affected by Vertex colors don't load #27 so while this PR will get it to load, vertex colors don't show up (will be a black point cloud).
• This PR doesn't include the binaries. If you want them for testing purposes, I have them on this branch: https://github.com/camnewnham/DracoUnity/tree/unity-point-clouds-v2-lib

Here's the same model with only the draco component (.drc)
bunny_pts_color.zip

In threejs:

In glTFast/Unity (this PR):

I'm not sure whether the lack of colors in this case is due to the same vertex color issue mentioned above or is something separate when using the glTF vs drc.

[atteneder]

Just like with #27 , the uint8 colors are the problem here:

On top of that (hacking in a uint8 to float conversion) I had to choose a different shader that supports vertex colored points. Looks like the shader decision has to consider the topplogy or maybe it's possible to add point support to the existing ones.

[atteneder]

Thanks for your contribution ❤️
I rebased this PR, fixed conflicts and added support for 2019.4.
The color issue remains, but there's the dedicated issue for it.

[camnewnham]

Thanks!

I had to choose a different shader that supports vertex colored points. Looks like the shader decision has to consider the topplogy or maybe it's possible to add point support to the existing ones.

I actually found atteneder/glTFast#228 because I was attempting to use the lack of PBR material as a hint to use a vertex-color unlit material. Instead, I ended up using a material name as the hint and when parsing the material in an IMaterialGenerator selected a vertex color compatible shader/material.

[atteneder]

Good solution! I imagined something similar.